Calculate the a/A ratio

CalcArterialAlveolarRatio.vb

Sub Main
	Console.WriteLine(CalcArterialAlveolarRatio(50, 60, 80))
End Sub

' Calculate the a/A ratio. Returns -1 if calculation not possible
' aARatio = 100 * PaO2 / (713 * FiO2 - PaCO2)
Function CalcArterialAlveolarRatio(dblPaCO2 As Double, dblPaO2 As Double, dblFiO2 As Double) As Double
	Dim dblRatio As Double = -1
	
	If dblFiO2 > 1 Then dblFiO2 = dblFiO2 / 100
	If dblPaCO2 > 0 And dblPaO2 > 0 And dblFiO2 > 0 Then
		dblRatio = 100 * dblPaO2 / (713 * dblFiO2 - dblPaCO2)
	End If
	
	Return dblRatio
End Function